New Thumbnail Service Functionality

[cxallan]

Given that rendering definitions are now available correctly and that thumbnail refreshes will start being requested we need the following methods for thumbnail refresh:

public void createThumbnails(Pixels pixels, RenderingDef def);

This method should refresh all thumbnails for a given user, for a given set of pixels regardless of their size.

Further, we also need methods to scale images into thumbnails based on the image's longest side:

public byte[] getThumbnailByLongestSide(Pixels pixels, RenderingDef def,
                                        Integer size);
public byte[] getThumbnailByLongestSideDirect(Pixels pixels,
                                              RenderingDef def,
                                              Integer size);

This method should scale the image proportionally. For example an image with a hight of 500 and a width of 100 where the "size" requested is 48, would scale the width by the ratio 48/500.

[cxallan]

Implemented in r1049.